"Biologists looking at 40 years of fisheries data from Puget Sound have documented a dramatic shift in marine species. Key fish in the food chain, like herring and smelt, have declined, while the number of jellyfish has increased exponentially, to the detriment of the marine ecosystem.

“On land people see the changes that come with human population increases, but underwater the changes are much harder to discern,” said Correigh Greene, with NOAA Fisheries’ Northwest Fisheries Science Center. “What this tells us is that when you look over time, you can see that the underwater landscape of Puget Sound is changing too,” said Greene, lead author of the new study published in Marine Ecology Progress Series.

The long-term study enabled the scientists to track parallel trends of rising human population and declining forage fish. The findings suggest a strong link between human influences such as pollution and development and the loss of species that were once common in Puget Sound. In particular, the rise of jellyfish blooms may divert energy away from highly-productive forage species that provide food for larger fish and predators such as salmon, seabirds and marine mammals."